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How to monitor your blood pressure

Updated: December 2018

Do-it-yourself testing

There are two circumstances in which you might test your blood pressure at home: because your doctor has asked you to, or because you want to keep an eye on it yourself. If you’re taking medication or making lifestyle changes to reduce your blood pressure, it can help you set goals and keep track of your progress – in fact patients who monitor their own blood pressure are more likely to be successful in their aims.

And if you’re one of those people whose blood pressure goes up whenever you walk in to a doctor’s surgery or hospital waiting room (a condition known as white-coat hypertension), measuring it at home can give a more realistic picture of what it’s like in more relaxed day-to-day conditions.

How does a blood pressure monitor work?

Blood pressure is measured using a sphygmomanometer, or blood pressure monitor. It consists of an inflatable cuff that’s wrapped around your arm, roughly level with your heart, and a monitoring device that measures the cuff’s pressure.

The monitor measures two pressures: systolic, and diastolic. Systolic pressure is higher, occurring when your heart beats and pushes blood through the arteries, and diastolic pressure is measured when your heart is resting and filling with blood. So, for example, your blood pressure might be 120 over 80.

Blood pressure monitors may be manual or digital, but home monitors are usually digital and the whole measurement process is automatic apart from placing the cuff around your arm.

The cuff then inflates until it fits tightly around your arm, cutting off your blood flow, and then the valve opens to deflate it. As the cuff reaches your systolic pressure, blood begins to flow around your artery. This creates a vibration that’s detected by the meter, which records your systolic pressure. In a traditional analogue sphygmomanometer, the blood sounds are detected by the doctor using a stethoscope.

As the cuff continues to deflate, it reaches your diastolic pressure, and the vibration stops. The meter senses this, and records the pressure again.

How to take blood pressure readings?

Taking readings requires some thought and preparation, though it will soon become second nature. There are several things to remember:

Relax. Steer clear of caffeine and exercise for thirty minutes beforehand, and rest for a few minutes. Sit comfortably upright with your feet flat on the floor and with your back supported.

Position your arm correctly. Rest it on a flat surface, with your upper arm level with your heart.

Position the cuff correctly, with the bottom edge just above your elbow.

The instruction manual of your device will also provide you with clear instructions.

When to check blood pressure?

If you’re using a blood pressure monitor on your doctor’s advice, he or she should tell you when to take readings. As a rule, though, you should take them at the same time of day on each occasion, so you’re comparing like with like.

Take a few readings each time, a couple of minutes apart, and calculate the average to make the figures more representative. And if your blood pressure monitor doesn’t store your readings for you, jot them down in a notebook to get an idea of long-term trends.